The Internet’s 24-hour shopping mall is now under scrutiny for the role it played in providing the suspect in the Colorado theater shooting access to bulk ammunition with little state, federal or human oversight.

While the national debate over gun control seems permanently stalled, the discussion over online sales of guns, bullets and other equipment could be revived by the Colorado shooting that left 12 dead and 58 injured.

Private gun sales, which often take place on the Internet, account for more than 40 percent of U.S. gun sales, according to a 2011 report by the office of the New York City mayor. The report found that in the past 15 years a significant share of gun sales has moved online.

At various stores online, and apparently without raising an eyebrow or a red flag, the suspect, James Holmes, was able to buy 3,000 rounds for an assault rifle, 3,000 rounds for Glock handguns and another 300 shotgun shells, according to The Wall Street Journal.

He also bought special equipment — a high capacity “drum magazine” — allowing him to hold 100 rounds. He had the ability to fire 50 or 60 rounds per minute, according to The New York Times.

That drum purchase would have been restricted by the Large Capacity Ammunition Feeding Device Act, federal legislation that has been stalled in the House. The bill, proposed by Rep. Carolyn McCarthy (D-N.Y.), whose husband was killed in a mass shooting on a commuter train in 1993, would put a ban on sales of magazines holding over 10 rounds.

“This needs to be a wakeup call,” she told constituents in Long Island over the weekend.

The National Rifle Association said in a statement that the group “believes that now is the time for families to grieve and for the community to heal. There will be an appropriate time down the road to engage in political and policy discussions.”

But the Internet may represent a new opening for gun control advocates, particularly when it comes to ammunition. There’s a patchwork of state weapons laws, with online retailers having to abide by the legislation where the buyer is physically located. Many online platforms, such as eBay and Craigslist, have prohibited weapons sales. Recently, Google announced it was banning gun and ammo sales on its shopping site.

Still, there are a vast number of private sellers who have moved on to the Internet.

“There are so few laws regulating ammunition that it may as well be the Wild West on the Internet,” said Laura Cutilletta, senior staff attorney at Law Center to Prevent Gun Violence. “The fact that it is removed and anonymous makes it easier for someone to amass large amounts of ammunition or someone who is not who he says he is.”

The online marketplace makes the job of enforcement tougher, particularly when it comes to private sellers of arms, gun control advocates say.

An investigation by New York City uncovered thousands of firearms for sale on Craigslist and compared the site to eBay where none were for sale. The report called for tougher self-policing protocols for websites where arms are sold.

But there is a hole in current law affecting online sales of ammunition created during the era of mail order sales, say gun control advocates. Before 1986, “the Colorado suspect could not have gone on the Internet and bought massive volumes of ammunition and had it been delivered to his apartment,” said Kristen Rand, legislative director at The Violence Policy Center.

The gun that shot President John Kennedy in 1963 was bought through the mail. That event led to the 1968 Gun Control Act outlawing interstate sales of guns and ammunition to unlicensed people, effectively shutting down the weapons and ammunition mail order business. That law was repealed in 1986 by the Fire Arms, Fire Owners’ Protection Act, also known as McClure-Volkmer, which among other things, deregulated ammunition sales and effectively opened up ammunition sales again.

Skip ahead more than 20 years to the online retail market. “No one could have foreseen this huge Internet market,” said Rand. “We need to reinstate some pre-existing law that clearly created a cascade of unforeseen consequences because of the rise of the Internet.”

Some states such as California and Massachusetts have regulated ammunition sales. A 2009 California law requires online handgun ammunitions sales to be competed through a face-to-face transaction with a licensed ammunition vendor.

Rand recommends that lawmakers consider instituting regulations requiring record keeping of ammunition sales and some kind of reporting to the Bureau of Alcohol, Tobacco, Firearms and Explosives if a large amount ammunition is purchased. “It seems like a no brainer,” she said.

This article first appeared on POLITICO Pro at 3:18 p.m. on July 23, 2012.